Atomic Mass: [1.00784; 1.00811] IUPAC guidelines 1.008 is commonly used for a single value

Electron Configuration: 1s1

Discovery: Henry Cavendish in 1766. Cavendish was the first to recognize hydrogen as an element. Others had prepared samples of hydrogen gas without identifying it as an element. Cavendish called his discovery ‘inflammable air’. Antoine Lavoisier suggested the name ‘hydrogene’ in 1783 and hydrogen was adopted soon after.

Name Origin: Hydro (Greek for “water”) Gene (Greek for “forming”). Lavoisier showed if you combusted hydrogen with oxygen, water was formed.

Common Isotopes:

1H Protium is the most common isotope. It has 1 proton and 1 electron. 99.98% of all naturally occurring hydrogen is protium.

2H Deuterium is 1 proton, 1 neutron and 1 electron. This isotope is commonly denoted by the letter D. The name comes from the Greek word “deuteros” meaning “second”. Approximately 0.02% of naturally occurring hydrogen is deuterium.

3HTritium contains 1 proton, 2 neutrons and 1 electron. This isotope si commonly denoted by the letter T. The name comes from the Greek word “tritos” meaning “third”. Trition is radioactive and decays by β decay into He-3 with a half-life of 12.32 ± 0.02 years. 10-18% of naturally occurring hydrogen is tritium.